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Questions tagged [turing-machines]

A Turing machine is an idealized model of computation consisting of a finite-state control, an infinite tape holding information, and a read head positioned somewhere over the tape. Turing machines are used in computability theory to reason about the limits of computation, to provide a formal definition for an algorithm, and to provide formal models for nondeterminism.

Wiki

A Turing machine is a device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a computer.

Turing machines are not physical objects but mathematical ones. A Turing machine is a kind of state machine. At any time the machine is in any one of a finite number of states. Instructions for a Turing machine consist in specified conditions under which the machine will transition between one state and another.

The tape is used to store data. In addition, it can also store a series of transitions (a small programs) and thus, the head can run sub-programs. By analogy with modern computers, the tape is the memory and the head is the microprocessor.

Tag usage

The tag can be used for programming related problems in implementing features of a turing machine. The tag can also be used for algorithmic problems related to turing machine. Try to avoid theoretical and research based questions on Stack Overflow.

Please note https://cstheory.stackexchange.com is another stack exchange website which you can use to ask theoretical and conceptual problems with tag

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Can Turing Machine work with decimal numbers?

I can do some operations on turing machine, but I use the binary forms of numbers, as the computers do. I wonder whether can I write decimal numbers on its tape and do calculation? Thanks in advance.
igelr
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How to construct this turing machine?

How can we construct TMs such that it accepts(Give description only): a + b = c a . b = c Input is of the form a#b#c. a,b and c belongs to {0,1}* and are positive binary unsigned integers. I know that we can construct TMs if the input has unary…
chelsea
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How to find a complement to the following language?

How to find complement of L, L = {: M is a TM, which accepts some palindrome} What is the general rule to finding a complement? I am thinking in this particular case it would be L_bar = { : M_bar is a TM, which rejects any palindrome…
acagu
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How to prove that the language $E_{tm}$ is $NP-Hard$

Consider the language $E_{tm}={ \langle M \rangle: M\text{is a Turing Machine that accepts nothing}$ I am not sure how to even start. My idea is to provide poly time reduction from some NP - Complete problem. E_tm What I don't understand is that,…
acagu
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Right Turing machine

I asked to check if Turing machine that can move only right (or stay) is equal to a standard Turing machine . I thought to copy the input to another tape, which unrestricted. but is it possible? thank u.
Tom
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Reducibility Etm undecideable

I want to ask about reduction. In the proof that Etm is undecideable in the definition of M1 is 1.if x!=w,reject 2.if x==w,run M on input w and accept if M does In many proofs that I meet I see that bold line but i can not understand how can I do…
A.Shoob
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Does a non deterministic turing machine solves a non deterministic algorithm in polynomial time

Can a non deterministic turing machine solve a non deterministic algorithm in polynomial time with good guessing. And if yes why or how? Also if not why not?
Vedad
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Prove that a specific language is not semidecidable

I have to prove that the language L = {< M >: |L(M)| <= 2016} is NOT semi-decidable. Now I thought of doing it like this: Take a random alfabet E. Now there are an infinite number of words in E. We can only conclude that |L(M)| <= 2016 by passing…
user4424299
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Proving Equivalence of TM and DFA

I'm trying to prove that TM = DFA is undecidable using reduction from Halting Problem Theoretically I understand that Turing Machine captures all the computable functions and DFA only capture the functions that can be computed in constant space…
Jake
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Compare numbers without deleting them - Turing machines

Is there a way to compare two binary numbers with a Turing machine without deleting them in the process?
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Turing Machine Configuration

I'm fairly new to Turing Machines and I'm stumped on a question. I'm given a Turing machine: M = (Q,Σ,Γ,δ,q) such that Q={q,r,s,t}, Σ={a.b.c}, Γ={B,a,b,c} and δ is defined by the following: [q,a,r,b,R], [q,b,r,a,R], q,c,t,c,R], [t,a,t,a,R],…
user4665295
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Running a function step-by-step to simulate a Turing Machine?

Just a random question - is there any way to run a Python function step by step? I want to be able to simulate things like dovetailing - where for each input I can run one step of the function at the time, so that it outputs all the return…
Arya
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Proof semidecidable languages

I have to proof "Semidecidable languages are closed by the direct morphism operation" I think that a direct morphism from E to F is a pair of morphisms s: E -> F, p: F->E, with p · s = IdE. So my porposal is make a proof with Turing Machines because…
Andrew Fells
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Turing Machine for regular languages

Theorem 5.3 from Sipser's TOC book is about decidability of Regular_TM = {M | M is a Turing Machines (TMs) and L(M) is regular languages}. For the sake of reaching a contradiction, TM R is assumed to be a decider for Regular_TM and then R is used to…
Mba7eth
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What is co-Turing recognizable, how do I prove complement of two languages is decidable using Co-Turing concepts?

Let L1 and L2 be two languages such that there exist no string w that belongs to both L1 and L2. I am struggling on How to Prove that, if L1 and L2 are both co-Turing-recognizable, there exists a decidable language A such that L1 ⊆ A and L2 ⊆ A`. A`…
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